657
FXUS65 KBYZ 292019
AFDBYZ
AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE BILLINGS MT
219 PM MDT FRI MAY 29 2026
KEY MESSAGES
- HOT TODAY. RIVER FLOWS INCREASE DUE TO MOUNTAIN SNOWMELT. NO
FLOODING IS EXPECTED AT THIS TIME.
- SLIGHT CHANCE OF LATE DAY SHOWERS AND THUNDERSTORMS TODAY.
ERRATIC WIND GUSTS UP TO 50 MPH, HAIL, AND HEAVY RAIN ARE THE
MAIN THREATS.
- WIDESPREAD SHOWER AND THUNDERSTORM ACTIVITY ALONG WITH A COOLING
TREND BEGINS SATURDAY. FLASH FLOODING RISK FOR RECENT BURN SCARS
INCLUDING THE ELK, ROBERTSON DRAW, AND THE EAST SIDE FIRES.
- ACCUMULATING SNOW IS FORECAST OVER 9000 FT THIS WEEKEND. WINTER
CONDITIONS MAY IMPACT THE BEARTOOTH HIGHWAY (MODERATE CHANCE).
- MARGINAL RISK (1/5) FOR STRONG TO SEVERE THUNDERSTORMS OVER
SOUTH-EASTERN MONTANA AND NORTH-EASTERN WYOMING SATURDAY.
DISCUSSION
TODAY THROUGH THURSDAY...
VERY WARM CONDITIONS PERSIST THIS AFTERNOON, WITH HIGH
TEMPERATURES FORECAST TO REACH INTO THE 80S TO LOW 90SF (WARMEST
IN EASTERN MT). ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS
ARE FORECAST THIS AFTERNOON. THERE IS A MARGINAL RISK FOR ISOLATED
STRONG TO SCATTERED THUNDERSTORMS THIS AFTERNOON OVER WEST-
CENTRAL MONTANA. FOR OUR AREA, THIS INCLUDES MUSSELSHELL, GOLDEN
VALLEY, AND WHEATLAND COUNTIES. THE PRIMARY CONCERNS WITH ANY
STORMS TODAY ARE ERRATIC WIND GUSTS UP TO 50 MPH AND HEAVY
RAINFALL. WITHIN THE MARGINAL RISK AREA, THE THREATS INCLUDE WIND
GUSTS UP TO 60 MPH AND HAIL. THE RISK FOR STRONGER TO SEVERE
STORMS IS LIMITED BY WEAK FORCING AND MINIMAL SHEAR ACROSS THE
FORECAST AREA. HIRES MODELS SHOW INVERTED V SOUNDINGS OVER THE
WEST-CENTRAL AREAS THROUGH 500MB FURTHER SHOWING THE RISK FOR
POTENTIALLY STRONG WIND GUSTS WITH ANY ACTIVITY. THE EASTERN
COUNTIES HAVE MUCH BETTER INSTABILITY WITH 1000-1800 J/KG OF
SURFACE CAPE AND SLIGHTLY BETTER BULK SHEAR. THE BREEZY ESE WINDS
OVER THE EASTERN AREAS WILL CONTINUE INTO THIS EVENING, BEFORE
DIMINISHING WITH INCREASING PRECIPITATION CHANCES. THERE IS A
DEFINED AREA OF CONVERGENCE AND WEAK FRONTOGENESIS SHOWN BY
MESOANALYSIS OVER SHERIDAN, ROSEBUD, CUSTER, AND POWDER RIVER
COUNTIES THIS AFTERNOON. CURRENT RADAR AND SATELLITE ANALYSIS
SHOW SHOWERS AND THUNDERSTORMS OVER THE BIGHORNS, MODELS DEPICT
FURTHER ACTIVITY DEVELOPING OVER THE AREA OF CONVERGENCE.
ADDITIONAL CONCERNS WITH ANY ACTIVITY THIS AFTERNOON AND EVENING
WILL BE WITH THE RECENT BURN SCARS INCLUDING THE ELK, ROBERTSON
DRAW, AND THE EAST SIDE FIRES. OTHERWISE, THE RISK OF FLOODING
REMAINS LOW ACROSS THE AREA.
AN UPPER LOW OVER THE GREAT BASIN WILL CONTINUE ITS TRACK
NORTHWARD INTO WYOMING ON SATURDAY. THIS WILL BRING WIDESPREAD
RAINFALL AND THUNDERSTORMS, AS WELL AS THE THREAT FOR A FEW STRONG
TO SEVERE THUNDERSTORMS IN SOUTHEAST MONTANA. A SURFACE LOW IS
EXPECTED TO DEVELOP OVER NORTHEAST WY, WESTERN SD, AND FAR
SOUTHEAST MT. COUNTIES INCLUDING AND EAST OF YELLOWSTONE COUNTY
ARE COVERED BY ANOTHER MARGINAL RISK (1/5) FOR ISOLATED STRONG TO
SEVERE THUNDERSTORMS. THE LOCATION OF THE UPPER LOW WILL PLAY A
BIG HAND IN WHERE STRONGER STORMS ARE ABLE TO DEVELOP. CURRENTLY
MODELS DEPICT THE BEST AREA OF UPPER DIVERGENCE OVER SOUTHERN MT
WHERE DECENT AMPLE FORCING ALONG WITH LONG SKINNY CAPE (UP TO 1000
J/KG) AND STEEP LAPSE RATES (>7.5 C/KM) EXISTS. NOTE, THE BEST
PARAMETERS WITHIN THE MARGINAL EXISTS ALONG THE DAKOTAS BORDER. IT
WILL BE TRICKY TO DETERMINE THE EVOLUTION OF STRONG TO SEVERE
THUNDERSTORMS GIVEN MORNING CONVECTION. ALTHOUGH MODELS DO SHOW A
BREAK INTO THE AFTERNOON DOWN THERE, ALLOWING FOR TEMPERATURES TO
WARM AND INSTABILITY TO REBOUND. THE PRIMARY THREATS ARE STRONG
WIND GUSTS UP TO 60 MPH, HAIL UP TO QUARTER SIZE, AND HEAVY
RAINFALL. WHILE THE RISK IS VERY LOW FOR TORNADOES, THERE IS A
CAVEAT TO THIS. DEPENDING ON THE LOCATION OF THE SURFACE LOW AND
THE MOVEMENT OF A BOUNDARY OVER WESTERN SD, THERE IS A BRIEF
WINDOW OF TORNADIC POTENTIAL NEAR THE LOW IN THE WARM SECTOR, IN
FAR SOUTHEAST MONTANA ALONG US-212 IN CARTER COUNTY.
THERE IS A MODERATE TO HIGH CHANCE FOR AT LEAST 0.5" OF RAINFALL
ACROSS THE REGION THROUGH MONDAY. FOR AREAS WEST AND SOUTH OF
MILES CITY THE CHANCE FOR AT LEAST AN INCH OF RAINFALL IS MODERATE
TO HIGH. THE LATEST FORECAST DEPICTS THIS. THE CHANCE FOR AN INCH
IS LOWER IN THE SOUTHEAST, INCLUDING FALLON, POWDER RIVER,
CARTER, AND SHERIDAN COUNTIES. BECAUSE OF THE WIDESPREAD RAINFALL
AND THE THREAT FOR HEAVY RAINFALL, FLASH FLOOD WATCHES HAVE BEEN
ISSUED FOR THE ELK, ROBERTSON DRAW, AND THE EAST SIDE FIRE,
SATURDAY MORNING THROUGH SATURDAY EVENING. THERE IS A SLIGHT RISK
(2/4) FOR EXCESSIVE RAINFALL CENTRAL MT TOMORROW. THIS CORRESPONDS
TO THE LATEST HREF 1"/HR RAINFALL PROBABILITIES OF 40-70% FOR A
POINT WITHIN 25KM. WHILE THE RISK FOR FLOODING REMAINS LOW OVERALL
AT THIS TIME, THERE COULD BE LOCALIZED CONCERNS DUE TO NEAR
STATIONARY THUNDERSTORMS AND HEAVY RAINFALL ON THE MENTIONED BURN
SCARS. PEOPLE NEAR BURN SCARS AND FLOOD PRONE AREAS SHOULD BE
ALERT AND THINK ABOUT A PLAN IF FLOODING OR DEBRIS FLOWS OCCUR.
A COLD FRONT IS DEPICTED MOVING THROUGH SATURDAY NIGHT, ALLOWING
FOR MUCH OF THE THUNDERSTORM ACTIVITY TO MOVE INTO THE DAKOTAS.
THE UPPER LOW HAS OTHER PLANS THOUGH, WITH ENSEMBLES SHOWING IT
PHASING WITH AN UPPER TROUGH OVER THE PNW. THE PRESENCE OF COOLER
AIR WILL BRING SNOW LEVELS DOWN FROM 11KFT TO AROUND 9KT BY SUNDAY
MORNING. ADDITIONAL SHOWERS AND WEAK THUNDERSTORMS WILL LINGER
THROUGH MONDAY, THOUGH SEVERE WEATHER IS NOT EXPECTED AT THIS
TIME. FOR THE MOUNTAINS, SNOWFALL ABOVE 9KFT IS FORECAST, WITH
SEVERAL INCHES OF ACCUMULATIONS ABOVE 10KFT. THE MAJORITY OF
ACCUMULATING SNOWFALL IS FORECAST ON SUNDAY, DIMINISHING INTO
MONDAY MORNING. BE PREPARED FOR POTENTIAL IMPACTS TO THE BEARTOOTH
HIGHWAY THIS WEEKEND.
AN AXIS OF BREEZY NORTHWEST WINDS LOOKS TO DEVELOP FROM WESTERN
MT SUNDAY INTO MONDAY. THE LATEST FORECAST HAS WINDS GUSTING IN
THE 25 TO 40 MPH RANGE, WITH GREATER GUSTS APPROACHING 50 MPH
ACROSS THE FOOTHILLS WEST OF BILLINGS.
FORECAST CERTAINTY DECREASES THE FIRST HALF THE WEEK AS ENSEMBLES
DISAGREE ON THE EVOLUTION AND PLACEMENT OF THE UPPER LOW.
CURRENTLY, THE ECMWF BRINGS ADDITIONAL WIDESPREAD PRECIPITATION
THE AREA INTO WEDNESDAY. MEANWHILE THE GEFS SHOWS LESS
PRECIPITATION. FOR NOW, THERE IS A LOW TO MODERATE CHANCE FOR
SHOWERS AND WEAK THUNDERSTORMS MONDAY INTO WEDNESDAY IN THE LATEST
FORECAST.
LOOK FOR HIGH TEMPERATURES IN THE 60S TO LOW 80S SATURDAY, UPPER
50S TO LOW 70S ON SUNDAY (COOLEST IN THE WEST EACH DAY), 60S TO
70F ON MONDAY, AND 70S TO 80SF THROUGH THE MIDDLE OF THE WEEK.
MATOS
AVIATION
UPDATED 19Z. ISOLATED TO SCATTERED SHOWERS/THUNDERSTORMS THIS
AFTERNOON AND EVENING ARE CAPABLE OF PRODUCING ERRATIC WIND GUSTS
UP TO 45KTS, LOCALIZED MODERATE RAINFALL AND BRIEF MVFR. VFR WILL
PREVAIL OTHERWISE TODAY. BREEZY SE WINDS (GUSTS 25-35KTS) WILL
CONTINUE INTO THIS EVENING OVER FAR EASTERN MONTANA (KBHK TO
K97M).
ON SATURDAY, A DISTURBANCE LIFTING OUT OF THE SOUTH WILL BRING
WIDESPREAD SHOWERS & THUNDERSTORMS, WITH ACTIVITY BEGINNING EARLY
IN THE MORNING. STORMS IN THE AFTERNOON/EVENING MAY PRODUCE STRONG
WIND GUSTS UP TO 40-50KTS, HEAVY RAIN AND UP TO 1" HAIL. GREATEST
POTENTIAL FOR SEVERE STORMS IS EAST OF KBIL. EXPECT AREAS OF MVFR
AND FREQUENT MOUNTAIN OBSCURATIONS TOMORROW. JKL
PRELIMINARY POINT TEMP/POPS
SAT SUN MON TUE WED THU FRI
-----------------------------------------------------------
BIL 059/069 052/061 047/067 048/073 049/077 052/081 052/086
28/T 87/T 52/T 22/W 11/B 22/T 21/U
LVM 049/062 042/053 039/063 039/071 041/077 045/078 045/083
38/T +9/T 64/T 22/T 11/U 24/T 21/U
HDN 055/074 049/064 044/069 044/075 046/078 050/081 049/087
27/T 78/T 62/W 31/B 11/U 22/T 21/U
MLS 058/079 052/071 045/067 047/075 049/077 051/082 053/085
26/T 68/T 64/W 41/B 21/U 22/T 21/U
4BQ 056/077 052/068 045/069 046/076 049/078 052/082 054/085
25/T 79/T 63/W 21/U 21/U 23/T 31/U
BHK 052/076 051/074 044/068 046/076 047/077 049/079 051/083
04/T 68/T 63/W 52/W 21/U 23/T 32/W
SHR 049/071 044/063 039/068 041/075 044/078 047/081 047/086
36/T 69/T 54/T 11/U 12/T 24/T 22/T
BYZ WATCHES/WARNINGS/ADVISORIES
MT...FLASH FLOOD WATCH IN EFFECT FROM SATURDAY MORNING THROUGH
SATURDAY EVENING FOR ZONES 56-67.
WY...FLASH FLOOD WATCH IN EFFECT FROM SATURDAY MORNING THROUGH
SATURDAY EVENING FOR ZONES 198-199.
WEATHER.GOV/BILLINGS
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